1. Field of the Invention
The present invention relates to an endoscope which is inserted into a hollow organ of the body undergoing examination. More particularly, the present invention pertains to a sheathed endoscope which is designed so that a portion thereof which comes into contact with mucus and mucous membrane in a hollow organ of the patient's body can be disposed of after being used for one endoscopic procedure.
To entirely prevent the transmission of bacteria and viruses from one patient to another through an endoscope, it is most effective to arrange an endoscope such that a portion thereof which comes into contact with mucus and mucous membrane in a hollow organ of the patient's body can be disposed of after being used for one endoscopic procedure.
Among various portions that constitute in combination an endoscope, those which come into contact with mucus and mucous membrane in a hollow organ of the patient's body include the outer surface of the insert tube and channels such as biopsy, air and water channels. Therefore, not only the skin of the insert tube but also these channels need to be made disposable so that they are disposed of after use.
2. Description of the Related Art
FIG. 4 shows a conventional sheathed endoscope wherein a U-shaped groove 52 is axially formed in the outer surface of an insert tube 51 of the endoscope and the outer surface of the insert tube 51 is covered with a removable sheath 53. Further, a channel tube 54 is fitted into the groove 52 from the outer side of the insert tube 51 so that both the sheath 53 and the channel tube 54 are disposable (see U.S. Pat. No. 4,646,722).
The above-described prior art suffers, however, from the following problems. Since the channel tube 54 is fitted in the U-shaped groove 52 formed in the outer surface of the insert tube 51, when the insert tube 51 is bent to have a small radius of curvature, the channel tube 54 protrudes outward from the groove 52; in some cases, the channel tube 54 comes out of the groove 52, which may result in damage to the channel tube 54 and the sheath 53. In addition, since it is essential for the insert tubes of endoscopes to have high torsional and crushing strengths as well as high flexibility, spiral tubes are generally employed for the insert tubes of endoscopes. In actual practice, however, it is almost impossible to form a U-shaped groove such as the groove 52 shown in FIG. 4 in the outer surface of a spiral tube. Accordingly, it has heretofore been impossible to produce a practicable flexible tube in regard to the structure in which a channel tube is fitted into the U-shaped groove 52 from the outer side of the insert tube.